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After nearly 30 years of arguing that a black hole destroys everything that falls into it, Stephen Hawking is saying he was wrong. It seems that black holes may after all allow information within them to escape. Hawking will present his latest finding at a conference in Ireland next week.

The about-turn might cost Hawking, a physicist at the University of Cambridge, an encyclopaedia because of a bet he made in 1997. More importantly, it might solve one of the long-standing puzzles in modern physics, known as the black hole information paradox.

It was Hawking's own work that created the paradox. In 1976, he calculated that once a black hole forms, it starts losing mass by radiating energy. This "Hawking radiation" contains no information about the matter inside the black hole and once the black hole evaporates, all information is lost.

But this conflicts with the laws of quantum physics, which say that such information can never be completely wiped out. Hawking's argument was that the intense gravitational fields of black holes somehow unravel the laws of quantum physics.

Other physicists have tried to chip away at this paradox. Earlier in 2004, Samir Mathur of Ohio State University in Columbus and his colleagues showed that if a black hole is modelled according to string theory - in which the universe is made of tiny, vibrating strings rather than point-like particles - then the black hole becomes a giant tangle of strings. And the Hawking radiation emitted by this "fuzzball" does contain information about the insides of a black hole (New Scientist print edition, 13 March).

Big reputation

Now, it seems that Hawking too has an answer to the conundrum and the physics community is abuzz with the news. Hawking requested at the last minute that he be allowed to present his findings at the 17th International Conference on General Relativity and Gravitation in Dublin, Ireland.

"He sent a note saying 'I have solved the black hole information paradox and I want to talk about it'," says Curt Cutler, a physicist at the Albert Einstein Institute in Golm, Germany, who is chairing the conference's scientific committee. "I haven't seen a preprint [of the paper]. To be quite honest, I went on Hawking's reputation."

Though Hawking has not yet revealed the detailed maths behind his finding, sketchy details have emerged from a seminar Hawking gave at Cambridge. According to Cambridge colleague Gary Gibbons, an expert on the physics of black holes who was at the seminar, Hawking's black holes, unlike classic black holes, do not have a well-defined event horizon that hides everything within them from the outside world.

In essence, his new black holes now never quite become the kind that gobble up everything. Instead, they keep emitting radiation for a long time, and eventually open up to reveal the information within. "It's possible that what he presented in the seminar is a solution," says Gibbons. "But I think you have to say the jury is still out."

Forever hidden

At the conference, Hawking will have an hour on 21 July to make his case. If he succeeds, then, ironically, he will lose a bet that he and theoretical physicist Kip Thorne of the California Institute of Technology (Caltech) in Pasadena made with John Preskill, also of Caltech.

They argued that "information swallowed by a black hole is forever hidden, and can never be revealed".

"Since Stephen has changed his view and now believes that black holes do not destroy information, I expect him [and Kip] to concede the bet," Preskill told New Scientist. The duo are expected to present Preskill with an encyclopaedia of his choice "from which information can be recovered at will".

Quote: After nearly 30 years of arguing that a black hole destroys everything that falls into it, Stephen Hawking is saying he was wrong.

Wrong,Hawking has presented the theory pointed out in the article since at least the late 80's. I guess he just has more mathematical proof of it now or something. He even mentions it in the extended version of A Brief History of Time .

From my understanding of his writing and other people's interpretations of his writings,he never really took a stance on whether or not so called "Hawking radiation" actually admitted information pertaining to the matter that falls into black holes. (Not counting his infamous set of encyclopedias against a subscription to Playboy bet with fellow physiacists)

Interesting none the less.I want to find out how the physics community reacts to his new mathematical proofs.

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The Euclidean path integral over all topologically trivial metrics can be done by time slicing and so is unitary when analytically continued to the Lorentzian. On the other hand, the path integral over all topologically non-trivial metrics is asymptotically independent of the initial state. Thus the total path integral is unitary and information is not lost in the formation and evaporation of black holes. The way the information gets out seems to be that a true event horizon never forms, just an apparent horizon.

Quote:He presented his ideas to physicists attending a conference on general relativity and gravitation in Dublin on July 21st. Using high-level mathematics, the language of theoretical physics, he revealed findings that contradict his earlier work. He says black holes never form an absolute event horizon?ie, a boundary from which nothing can escape. Rather, they form an apparent horizon.

Blurring this boundary means that information can eventually get back into our universe. So, when the black hole dies, it opens up its secrets not to a parallel universe but to our own. As the information returns, albeit in a mangled form, this reconciles the information paradox.

Black-hole physics has provided fodder for science-fiction stories for years. When announcing his findings, Dr Hawking was apologetic about his news, ?I'm sorry to disappoint science-fiction fans, but if information is preserved, there is no possibility of using black holes to travel to other universes.?

Physicists have been trying to chisel away at the paradox for many years with little success. It is Dr Hawking's remoulding of his own work that has been responsible for resolving the wager made in 1997. Dr Preskill has now won, as Dr Hawking said the information paradox would hold. The published terms of the bet were that the loser would award the winner with a set of encyclopedias from which ?information can be recovered at will?. Dr Preskill is the proud new owner of an encyclopedia of baseball.

Quote:"I'm sorry to disappoint science fiction fans," Hawking, speaking via a specially-constructed computer, told a conference of 600 scientists from 48 countries, "but ... there is no possibility of using black holes to travel to other universes.

"If you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form," he said, drawing laughter from the crowd.

"It's great to solve a problem that has been troubling me for nearly 30 years, even though the answer is less exciting than the alternative I suggested," added Hawking.